Hub-type telegraph repeater concentration group signaling



Jan 7 1947' A. R. BONORDEN ETAL. 2,413,588

HUB TYPE TELEGRAPH BEPEATER CONENTRATION GROUP SIGNALING Original Filed Oct. 24, 1940 .6 Shees-Sheefr. 2

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Il ARBONORDEN RV/@2s f/vvENToRs--JAK CEK @Y We l ATTORNEY `Fam. 7, 1947.' A. R, BONORDEN ETAL 2,43533 HUB TYPE TELEGRAPH REPEATER CONCENTRATION GROUP SIGNLIHG e Smets-sheet s original Filed oct. 24, 1940 cg( TAmARsHALL v... E

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INVENTORS Erf/Q k Nm. ,Si Q shui ATTORNEY 5am, w47.' A. R. BONORDEN 5TMA 254332588 HUB TYPE TELEGRAPH REPEATER CONCENTRATICN GROUP SIGNALIG Original Filed Oct. 24, 1940 6 Sheets-Shee 4 N L L M KA Y R EEH E 0566s. N 0% m wwf/Mc n RVMAMA APJM 5., n R y m a m. V. w

Jan-7, w47 A. RBONORDEN ETAL 2,413,688

HUB TYPE TELEGRAPH REPEATER CONCENTRATIONLGROUP SIGNALNG' original Filed oct. 24, 1940 e 'sheets-sheet 5 ATTORNEY Patented Jan. 7, 1947 UNITED sTATEs PATENT oEElcE HUB-TYPE TELEGRAPH REPEATER CON- CENTRATION GROUP SIGNALING New York Original application October 24, 1940. Serial No.

362,548. Divided and this application November 16, 1943, Serial No. 510,486

This invention relates to telegraph systems and more particularly to telegraph systems wherein private branch lines are associated together, in local, state-wide, or nation-wide networks on a semipermanent basis as distinguished from a telegraph exchange switching system. This is a division of copending application Serial 362,548 led October 24, 1940, now Patent No. 2,349,586, granted May 23, 1944.

An object of this invention is the improvement of arrangements for associating telegraph circuit elements, such as lines and station loops in telegraph networks on a semipermanent basis, in order to facilitate additions to and subtractions from the network and to facilitate the substitution of new circuit elements for existing circuit elements, as well as the testing of' the various circuit elements in telegraph networks.

Another object of this invention is the provision of means to enable a patron connected through a switchboard into a concentration` group of inverse neutral, or hub type repeaters as they are known, to attract the attention of an` attend- 14 Claims., (Cl. 178-69) ant at the switchboard when changes in the network may be required.

Another object of the invention is the provision of means to enable an operator to identify telegraph lines or trunks extending to distant cities which are available for connection into a concentration hub type repeater when such a facility is required.

The operation of telegraph systems wherein private telegraph lines are associate-d together into networks which remain interconnected for indenite periods has heretofore been characterized by a lack of flexibility. That is to say, the addition to the network, or the subtraction from the network of telegraph lines or lstation loops, or the substitution in the network of one telegraph line or station loop for another, required compensatory adjustments of one or more of the telegraph repeaters in the network, because the repeaters weer arranged in series and the current in the various repeaters was affected when the resistance was changed as the network was altered. Furthermore, added repeaters had to be adjusted to provide the proper polarity as well as type of operation, such as half or full duplex operation.

To overcome this difficult a new type of telegraph repeater was devised, which provides what is known as the inverse neutral type ot transmission on the drop side, for use primarily in service where private telegraph lines were associated, in networks on a semipermanent basis. The operation of such inverse neutral repeaters is described in Patents 2 056.277, F. S. Kinkead et al.. October 3, 1936, 2,069 224. G. C. Cummings, February 2, 1937, and 2,069,251, F. S. Kinkead, February 2, 1937.

When circuit elements of a private line network appear in a telegraph cnice in which the new inverse neutral repeater is used, as described in the above-mentioned patents, each telegraph station loop and telegraph line is connected into what is known in the art as a concentration group through its own individual inverse neutral repeater. The drop sides or legs of all of the line repeaters and station loop repeaters are interconnected through a common point, which is otherwise known as the hub of the concentration group. From this common point or hub, the leg of each line repeater and station loop repeater extends in series through the armature and marking contact of a receiving relay and through the winding of a sending relay to negative battery common to all repeaters. This common battery has its positive terminal grounded. No current flows through the various legs of a concentration group during the marking condition. For the spacing condition, the armature of the receiving relay in a particular leg is actuated to engage with a grounded contact. This causes current to flow through each of the other legs toward and through the hub point to ground through the single spacing contact. A sending relay having a winding in series in eachof the other legs is energized to transmit the spacing signal to the circuit connected to each of the other legs in the same concentration group.

For the full duplex condition two independent hubs are provided, as it is impossible to transmit in two directions simultaneously through a single hub. The transmission in each set of connected legs is otherwise the same as for the half duplex condition.

It may be observed, therefore, that in the use of inverse neutral repeaters the legs of the various repeaters, when joined in a concentration group, are all connected in parallel. One end of each leg is joined at the common electrical point or hub. The other end of each leg terminates in battery of the same potential and magnitude for marking. Any repeater when sending toward the hub connects ground to the hub point and transmits signals simultaneously to all other legs in the concentration group. The signals are openand close or neutral signals, as they are known in the art, but they are inverted from the usual, in that the marking signals are Aiiows for this condition, and since, electrically,

groundis connected, as a practical matter, di-

rectly to the hub point for the spacing condition,l

the current conditions in any leg when it is receiving from the hub, are unalfected by the addition or subtraction of another leg to the concentration group or by the substitution of a different leg for any leg forming part of a concentration group. When transmitting toward the hub, the only effect is a change in magnitude of spacing current in the transmitting leg, from the single spacing contact to the hub point, as the number of connected legs is changed.

When the circuit elements of private telegraph line networks are arranged so that each includes its own inverse neutral telegraph repeater and becomes, for the purpose of association into a network, an electrically independent unit, it is possible to terminate the legs of line repeaters and loop repeaters in a switchboard and to make such changes in private line concentration groups as may be necessary, simply by a switching or patching operation at the switchboard, without the necessity for making poling or current adjustments in the leg side of the various repeaters in the concentration group to accommodate such changes. As will be shown later, the type of operation, viz. half or full duplex, of any line repeater is automatically effected at the time the repeater is patched.

In one of its major aspects, therefore, this invention is a switching system for inverse neutral telegraph repeater circuits, adapted to exploit the inherent characteristic of inverse neutral repeaters that, for the purpose of association in concentration groups, each telegraph line or loop leg, equipped with an inverse neutral repeater, is electrically an independent unit.

In this invention, control circuits are arranged to adapt inverse neutral repeater circuits, as used in semipermanent concentration groups, so that they may be controlled at telegraph switchboard positions. To this end, telegraph line circuits extending to telegraph central offices in distant cities are equipped with inverse neutral repeaters and their legs are extended through leg multiple jack circuits, which provide a jack appearance within reach of each attendant in the line-up of switchboard positions. This makes every telegraph line facility available, through the medium of a jack outlet, to every switchboard attendant in the switchboard line-up. The line side of the line repeater circuit is adjusted once for all, so as to provide the optimum signaling conditions. Since the leg of each line circuit in the board is equipped with an inverse neutral repeater, and is, therefore, an independent entity electrically, it may be used to communicate with the distant central oflice as a separate facility. Or it may be added to a network without the necessity for compensatory adjustments on the leg side.

In this invention, an appearance of a particular private line network may include a number of station loops, extending from various points 4 in the local area Where one of the switchboard line-ups of this invention is assumed to be located, into the switchboard. Each of the local station loops will have an independent inverse Vneutral loop repeater connected to it. Each leg of such loop repeater will be terminated in a particular position in the board in a group of three jacks which will be termed hereafter loop concentration jacks. All of the jacks associated with loop circuits which are to be formed into a particular concentration group will appear, preferably side by side, at some one position in the switchboard line-up, so that the loop circuits may be administered by an attendant at that position. The loop jacks may be multipled to a second position, so that at times, a second attendant may supervise the concentration group. The line circuits, the repeater legs of which, as has been pointed out, are multipled throughout the board, must be interconnected to the loop circuits so that the concentration group may be extended to other portions of the network appearing in switchboards in distant cities as required. This is done by selecting the proper line facilities from the entire group which are multipled throughout the board and extending the leg of each one which is required into a group of three other jacks, termed line concentration jacks, each group of jacks being individual to a line circuit at the particular position where the concentration group is to be administered. The legs of each of the loop and line repeaters which are to be associated in a particular concentration group, after passing through its, individual group of jacks at a particular attendants position, are all joined in a common electrical point which becomes the hub of the concentration group.

The connecting together of the individual leg conductors to form the hub may be effected in any convenient manner. In order to reduce the possibility of disconnecting any line or loop inadvertently from a concentration group with which it is normally associated, the individual conductors may be extended to individual punchings on a terminal strip and strapped together with a common soldered connection. When thus assembled, the line circuits and loop circuits in a concentration group each have groups of jacks, individual to each line circuit and loop circuit, all of which appear before a particular attendant in the switchboard line-up who is responsible for the administration of the service. Since, as has been pointed out above, all of the telegraph lines from distant cities, which come into the telegraph'oce where the switchboard of this invention is assumed to be located, are each equipped with an individual inverse neutral repeater which makes it an independent entity and each line has an appearance, in the form of a multiple jack, within cord reach of each attendant, any idle line in the multiple may be connected on a temporary basis into a particular telegraph network by a patch from the multiple at the position into one of the concentration jacks .at the particular position where the concentration group for that network appears. It is to be understood, of course, that the bank of line leg multiple jacl extending through the switchboard are terminations of circuits which extend to many different cities and itis necessary to select one extending to the proper destination. This may be determined from reference to the jack designation strip.

The normal network, as required'to provide the proper number of telegraph lines to distant cities and the proper number of. loops to stations in the local area served by the switchboard of this invention, will be set up in what is essentially a permanent concentration group.. Each line and loop leg will be extended through its own individual group of concentration jacks in the switchboard position where the concentration group is to be administered and joined together in a hub, preferably by a soldered connection. The jacks in the various individual line and loop legs provide means for making changes in the network as required on a temporary basis by means of patches. They also provide means for testing, monitoring, measuring bias, communicating with the attendant, etc., and, in general, permit the complete administration of the various private line. networks, the testing and supervision or" the elements of a network, the addition of lines or loops, the disconnection of a line or a loop or the substitution of a new line or loop for one forming part of a network. All or this may be performed by an attendant seated at a switchboard. As pointed out above, since the leg of each line and loop is equipped with its own individual inverse neutral repeater, these additions, subtractions and substitutions may be made without the necessity for making any compensating adjustments in the network or in the individual repeaters.

The invention may be more fully understood from the following description when read with reference to the various associated drawings in which:

Fig. 1 representsv two four-wire full metallic telegraph line circuits, equipped with inverse neutral line repeaters, arranged for conversion from full to half duplex operation when connected to full or half duplex concentration groups;

Fig. 2 represents two telegraph station loop circuits equipped with two inverse neutral loop repeaters and two sets of loop concentration jacks, for connecting two local stations into a hall duplex concentration group;

Fig. 3 represents two line leg multiple circuits and two sets of line vconcentration jacks, the last f mentioned for use in terminating two lines arranged for half duplex operation and includes a station calling-in circuit by means ci which a station attendant may call an attendant at a service board;

Fig. Il represents an idle indicator' control circuit for controlling lamps which momentarily indicate all idle lines to remote points, in response to the actuation of a key by an attendant who l requires a new line, to enable the attendant to i' quickly select a line to a particular distant terminal for connection toa concentration group;

Fig. 5 represents a splitting circuit which is used with a telegraph cord circuit for testing lines before the lines are connected to a concentration group;

Fig. 5A represents a telegraph cord circuit for use in connection with Fig. 5 for testing lines before adding them to a concentration group;

Fig. 6 represents a local station connected through two separate loops to two inverse neutral loop repeaters and two sets of loop concentration jacks, for use in full duplex operation;

Fig. 7 represents two leg multiple circuits and four sets of line concentration jacks for use in terminating two lines to remote terminals arranged for full duplex operation.

The rectangle A bearing the legend Half duplex concentrationgroup indicates the manner in which Figs. 1, 2, 3 and 4 are assembled to form a half duplex concentration group, comprising two lines to two distant terminals and two local station loops, at the telegraph service board.

The rectangle Fig. B bearing the legend Full duplex concentration group indicates the manner in which Figs. 1, 4, 6 and 7 are assembled to form a full duplex concentration group comprising two lines interconnected through a telegraph service board, as the switchboard ci this invention is known to provide full duplex operation between two remote terminals. 1t shows also a single patrons station in the local area served by the telegraph service board, connected through two loops into the full duplex line to provide full duplex operation between the local station and the two remote terminals.

HALF DUPLEX CONCENTRATION GROUP A half duplex concentration group will rst be described.

Figs. l, 2, 8 and 4 are arranged in relation to each other as indicated in the, rectangular block diagram Fig. A, bearing the legend, Half duplex concentration group. As thus arranged, they constitute a concentration group, comprising two telegraph line circuits and two telegraph loop circuits, together with a calling-in signal circuit and an idle indicator control circuit. rl'he telegraph line and loop circuits are connected together at a telegraph central cnice, through a new telegraph facility to be known as a telegraph service board. The operation of the fundamental switching circuits of this new board are to be described herein.

From the oiiice where the telegraph service board is located, one telegraphline circuit is assumed to extend to a telegraph central oice to the east and the second to a telegraph central cnice to the west. One loop connects a local telegraph station designated A, of a first patron, in the same local area as that in which the service board is located into the concentration group at the service board. The secondloop connects a local telegraph station, designated B, of a second patron, also in the same local area as that in which the service board is located, into the same concentration group at the service board.

The circuits are arranged to form a half duplex telegraph concentration group. By this is meant, in this instance, that either loop station may send telegraph signals which are transmitted to the other loop station and over the line east and line west simultaneously, or either line may send telegraph signals which are transmitted to each loop and over the other line simultaneously. It is not possible, however, for any station to receive from other stations while it is sending.

In the description of a halfduplex concentration group, apparatus in the circuits for station A and the east line will be designated by numbers only. The letters B and W will be added to corresponding apparatus in the circuitsfor station B and the west line respectively.

The manner in which a loop station transmits to 'the other loop and to the two lines simultaneously will first be described. It will be assumed that loop station A transmits. To do this the shunt 20|, which short-circuits the transmitting contacts at station A when the circuit is idle, will be opened and the contacts of keylz will be closed so thaty the transmitting key 202 may take control of thev circuit.

The armature of relay 22 is heldin engagement with its left-hand or marking contact by the eilect of current flowing from battery 2l6 Vsponding manner.

7 through resistance 211 and the top winding of relay 212 to ground. No current flows through the bottom winding of relay 212 for this condition as will be explained below.

When the transmitting key 202 is closed, a circuit may be traced from ground through positive battery 203, through resistance 204, through resistance 205, through the bottom Winding of relay 206, through the tip and break contact of jack 201, through the break contact and ring of jack 208, through the variable resistance 226, normal make contacts of call signal key 221, through the winding of the sounder 209, through the closed contacts of key 202, through the tip and break contact of jack 208, through the break contact and ring of jack 201, through the to-p Winding of relay 206, through the top winding of polar relay 210, through inductance coil 21 I, through the armature of relay 212, through resistance 213, through negative battery 214 and back to ground. .Positive and negative battery are thus connected to the two ends of the loop circuit and current flows, for the marking or closed condition, through the loop circuit. The effect of the current flowing through the top winding of relay 210 tends to actuate the armature of relay 210 to engage with its right-hand or marking contact. It preponderates over the eiect of current flowing through the bottom winding of relay 210, over a circuit from ground through negative battery 214, through resistance 213, through the left-hand or marking contact i and armature of relay 212, through inductance coil 211, through the bottom winding of relay 210 and resistance 215 to ground, which current tends to actuate the armature of relay `210 to engage with its left-hand or spacing contact and the armature of relay 210 is thus maintained :in engagement with its right-hand or marking contact.

Relay 206 is so arranged that when current iiows through both its top and bottom windings, as is the case when the loop is closed, the eiect in one Winding is balanced by the eiect in the `other winding and its armature remains in its f.-

normal unoperated position as indicated.

When the armature of relay 210 is inengagement with its right-hand or marking contact, it connects negative battery to the hub of the concentration group. The circuit for this may be traced from battery 216, through resistance 218, through the bottom Winding of relay 212, through the right-hand or marking contact and armature` of relay 210, through test resistance 219, through the top back contact and armature of relay 220, to conductor 221. Conductor 221 may be considered electrically as a point which constitutes the hub of the circuit.

Station B is joined into the hub in a corre- For the marking condition, station B connects negative battery, indicated 216B, over a path similar to that traced for station A, which passes ultimately through testing resistance 219B to hub 221.

The manner in which one of the telegraph lines is connected into the concentration group will now be explained. The circuit of the line east will be used for this purpose. This telegraph line is a four-wirev metallic circuit. Its operation is described in detail in the application of R. B.

Hearn, Serial No. 342,431, ledvJune 26, 1940.

As therein described, the circuit may be arranged vto function either half duplex or full duplex dependent upon whether it is connected into a full duplex` or a half duplex concentration group. AIn

this instance it is connected into a half duplex concentration group andtherefore is arranged to function half duplex.

Refer now to Fig. 1 Which shows in detail a four-Wire metallic telegraph line connecting a distant telegraph central oflice, located, it is assumed, to the east, into the concentration group at the oiiice Where the concentration group is established and which indicates diagrammatically, by a rectangular box, an identical telegraph line for the telegraph line west which, it is assumed, connects a central oice located to the west into the concentration group. Although a four-Wire metallic circuit is shown for this purpose, carrier line circuits, one-way polar circuits, and other line circuits, when terminated in proper inverse neutral type repeaters, may be used in place of the four-wire metallic line and the associated inverse neutral repeater shown.

The upper two line conductors of Fig. 1 constitute the path over which the distant repeater to the east receives from the concentration group. The lower two line conductors of Fig. 1 constitute the path over which the distant repeater to the east transmits into the concentration group.

Relays 101 and 102 are polar relays in the transmitting circuit at the distant central oiice. When the armatures of these relays are in the positions indicated, Which is for the marking condition, a path may be traced from ground through battery 103, through resistance 104, the left-hand contact and armature of relay 101, through inductance coil 105, the top winding of polar relay 10B, the armature and right-.hand contact of relay 102 and through resistance 101 back to ground. Apparatus corresponding to coils 124, and 126 together with the associated condenser may be inserted, if desired, in this path at the distant central terminal, in the same manner as they are connected in the two top conductors of Fig. 1. The function of this apparatus is to suppress noise caused by telegraph thump on the telephone circuit operated over the same pair of cable conductors. The effect of the current in the top winding in the path traced above is to operate the armature of relay 106 into engagement with its right-hand or marking contact. The operation of the circuit through the bottom Winding of relay 106, known in the art as a vibratory circuit, is to tend to speed up the action of the relay. It is well known in the art and will not, therefore, be described herein in detail.

When the armature of relay 10:` is in engagement with its right-hand or marking contact, a circuit may be traced from ground through negative battery 103, through resistance 109, through the right-hand or marking contact and armature of relay 10B, through resistances 110 and 111 and through the top winding of polar relay 112 to ground. The effect of this current is to a-ctuate the armature of relay 112 into engagement with its right-hand or marking Contact. No current flows through the bottom winding of relay I 12 for this condition as the circuit through the bottom winding of relay 112, connects at one end to the hub 221 of the concentration group andA at the other end to negative battery. 'Ihis circuit may be traced from negative battery 115 through resistances 116 and 111, through the bottom windings of polar relays 1 1S and 1 15, .fthrough the lefthand armature and front contact of relay 113, through the bottom Winding of relay 1 12, through the right-hand front contact and armature of relay 113, through the right-hand or marking .Contact .and armature of relay 112,'th'rough1eg conductor |20, through Fig. 2 into Fig. 3 .to parallel branches. One branch continues through the top armature and back contact of relay 30|, through test resistance 303 and the back contact and armature of relay 304 to the hub 22| of the circuit. rihe other branch extends in multiple through the tips of the multiple jacks 3I6, 3H, 3|8, etc., one of which is accessible at each position in the telegraph service board of this invention.

A biasing circuit for relays IEB and IIS may be traced from b-attery IIE, through resistance l2@ and the tcp windings of relays |I8 and |I9 to ground. The effect of this lcurrent tends to actuate the armatures of relays I I8 and I I9 to engage with their right and left-hand contactsl respectively for the marking condition. This effect is not opposed as there is no current ilowing through the bottom windings of these relays for the marking condition of the concentration group, since all of the legs of the concentration group .terminate in battery of the same polarity for the marking condition.

The loop over which the distant oice to the east lreceives may be traced from ground, through battery l2! to its positive terminal, through resistance E22, through the left-hand or marking contact and armature of relay IIS, through .the bottom winding of inductance coils |24 and |25, through the 'bottom winding of repeating coil |28, through'the bottom line conductor to the distant terminal, through the winding of the receiving relay |27, through the top line conductor, through the .top windings of the repeating coil |26, through the top windings of inductance coils |25 and |1243, through the armature and righthand or marking contact of relay II and resistance |35 to ground.

The four-wire line to the west indicated by the rectangular box at the bottom of Fig. 1 is arranged in the identical manner as that described for the four-wire line to the east. It connects negative battery of the saine magnitude as battery i I in the east line through an identical circuit to leg conductor I3I, -which corresponds to lconductor 29 of the east line, through the top outer armature Aand back contact of relay 3.0IW and test resistance 3%3W, through the back constact and armature of relay 324W to hub 22 I.

Thus each line leg and each loop leg connects negative battery of the same magnitude to the hub of the concentration group for the marking condition.

If `a lspacing signal is transmitted from :any station loop circuit or from any telegraph line forming part of the concentration group, theleg o1" the circuit transmitting the spacing signal will be connected to ground which grounds the hub and operates a relay in each of the other legs to transmit the spacing signalinto each of the other connected circuits. The manner in which this is performed will ynow be explained.

It will be assumed that the operator at station fi opens the conta-cts oi the transmitting key 202 to send a spacing signal. This breaks the loop circuit for station A, heretofore traced. The top winding of relay 2|@ is deenergized. The armature ofrelay 2HE is actuated, under the influence of current through its bottom winding, to engage with its left-hand or spacing contact which is grounded. This disconnects negative battery 2 I5 from the leg -whichfextends through resistance 2 I 9 into the hub 22| and connects ground through .resistance 2li@ to hub'22'I.

When ground is connected to the hub, acircuit may be traced from hub 22l through the upper armature and back contact of relay 220B, through test resistance ZISB, through the armature and right-hand or marking contact 0i relay 2 IBB, through the bottom winding of relay 2l2B and resistance ZIBB, to battery 2I6B, The -eiect of this current flowing through the bottom winding vof relay 2l 2B preponderates over the elect of current flowing through the top winding of relay v2I2B which has been holding the armature of relay 2|2B in engagement with its left-hand or marking contact and the armature of relay 2I2B is actuated to engage with its right-hand or spacing Contact.

Loop B is arranged in the identical manner described for loop A. When loop A was traced it was shown that the two ends of the loop terminated in battery of opposite polarity for the marking condition. Similarly, the two ends of loop B terminate in battery of the opposite polarity for the marking condition. When, however, the armature of relay 2I2B is actuated to engage with its right-hand armature, negative battery is disconnected irom one end of the loo-p and both ends are terminated in positive battery of the same magnitude so that no current flows in the loop. The sounder 269B at station B is deenergized and a spacing signal is received at station B.

The manner in which the same spacing signal is received at the east central telegraph terminal will now be explained.

When the spacing signal is received in the hub from station A, ground, as has been shown, is connected through resistance 2 I 9 to hub 22| and a circuit may be traced through the armature and back contact of relay 30d through testing resistance pthrough the top outer back Contact and armature of relay 30|, through leg conductor |20, through Fig. 2 into Fig. l, through the armature and right-hand contact of relay .I I2, through the right-hand armature and front Contact of relay H3, through the bottom winding of relay II2, through the left-hand front Contact and armature of relay I I3, through the bottom windings of relays IIS and H8, thro-ugh resistances III and i E and battery I Iii to ground. The effect of current flowing in the bottom windings of relays I I9 and H6 for this condition is such that it tends to actuate the armature of relay II'S to engage with its right-hand contact and the armature of relay IIB to engage with its left-hand Contact and this `effect preponderates over the effect of the current flowing through the top windings, so the armature of relay IIS is actuated to engage its right-hand contact and the armature of -relay I I3 is actuated to engage its left-hand contact.

When the armatures of relays II9 and II8are actuated as described in the foregoing paragraph, the polarity of'battery |24 in relation to the two 'ends of the east send line through the receiving relay at the distant ofce will be reversed. That this is so may be understood by observing that there are two conductors extending from each 4of resistances |22 and |30 respectively. One .conductor extends from each resistance to contacts which are in engagement with the armatures of relays IIB and IIB when their armatures are in the positions shown in Fig. 1 and one conductor extends from each of said resistances to a contact on the other of the relays with which each armature makes engagement when in the spacing condition. Thus as the two relays IIS and IIB respond to a spacing signal, the polarity of battery I2I connected to the ends of the line for the vmarking lcondition is reversed, resulting in a spacing signal being transmitted to the distant receiving relay |21.

The spacing signal originating at station A is transmitted t the distant receiving relay connected to the West line in the same manner as described above for the east line.

Thus as the armature of the relay 2li), which receives from station A and transmits toward the hub, is actuated so as to connect ground and negative battery alternately to the hub 22|, the armature of the receiving relay in the inverse neutral repeater of each of the other legs connected to the hub, whether it be a loop leg or a line leg, is operated simultaneously to transmit spacing and marking signals into its loop or line.

When signals are transmitted from a distant oii'ice over a telegraph line, it will be assumed over the east line, relays lill and |62 in the distant oiiice are operated from a connected circuit not shown. This reverses the connections between the two conductors of the bottom two-wire line and battery |3. Relay |06 is in turn actuated. As the armature of relay |86 is actuated between positive and negative battery, relay l2 responds. As the armature of relay I l2 is actuated, negative battery and ground are alternately connected to hub 22| and marking and spacing signals are impressed upon all other legs forming part of the concentration group.

In the same manner signals may be transmitted from the distant western cnice over the west line into its respective inverse neutral repeater and thence to the hub to actuate the sending relay in each individual inverse neutral repeater in each other leg whether loopor line.

From the above description it should be apparent how any loop or telegraph line may transmit marking or spacing signals to all telegraph circuits forming part of a half duplex concentration group.

Breaking operatz'on in a duplex conentration goup It is possible to transmit a break signal from any circuit connected into a half duplex concentration group, to prevent any circuit which is transmitting to the other circuits of a concentration group from continuing to transmit. The manner in which this is performed will rst be described for the condition in which signals are being transmitted from the distant oiiice over the east line and the attendant at loop station A breaks.

When signals are lbeing transmitted from the distant oice over the east line, it has been shown that relays |06 and ||2 follow the signals to connect ground and negative battery alternately to hub 22|. If the attendant at station A wishes to stop the transmitting from the east line, so that station A may transmit, key 292 is opened and is mainained in the open condition. The opening of key 202, as has been described, results in ground being connected to the hub when relay 2|2 next closes its marking or right-hand contact. Since the key 202 is maintained open, a permanent ground is connected to the hub resulting in a permanent spacing signal being transmitted from the hub out over each connected leg. In the case of the line which is receiving signals from the distant oii'ice, if the armature of relay |2 is in engagement with its left-hand or spacing contact, in response to a spacing signal transmitted from the east line toward the hub, nothing will happen momentarily in its send side, as

ground from the hub will be connected to one of conductor |29 and it will meet ground on the left-hand or spacing contact of relay |l2. As soon as the armature of relay ||2 is actuated to engage withits right-hand contact, however, the ground from the hub will be conected to one end of the path through the bottom windings ol sending relays ||9 and H8 and battery ||5 will be connected to the other end and over the circuit heretofore traced. Under this condition the armature of relay ||2 is maintained in engagement with its right-hand Contact, as the effect of the current owing through the bottom winding of relay H2, tending to actuate the armature of relay ||2 toward the right, preponderates over the eiitect of spacing signal current from relay |03 tending to actuate the armature of relay ||2 toward the left. Relays ||8 and ||9 will be operated when the armature of relay ||2 is on its right-hand contact, from ground connected to the hub. With the armatures of relays ||8 and ||9 actuated to their spacing contacts, a permanent spacing signal is transmitted toward the distant ofce to the east as a breaking signal.

If either loop sttaion is transmitting, any line or the other loop may break. It Will be assumed that station A is transmitting and that the east telegraph line breaks. This is performed in the following manner. A permanent spacing signal is transmitted from the east telegraph terminal into the hub, operating relay |86 to its left-hand or spacing contact. This Will operate relay ||2 to spacing when relay 2li) next closes its right or marking contact to remove ground from hub 22 This results in the connection of Ipermanent ground to hub' 22| from the left-hand contact and armature of relay ||2. A circuit may be traced from the grounded hub 22|, through the armature and back contact of relay 22D, through resistance 2|9, to the armature of relay 2|0. If the armature of relay 2|0 is again in engagement with its left-hand or spacing contact, nothing happens momentarliy. When the armature of relay 2|@ next engages its right-hand contact,

the circuit will be extended through the bottom winding of relay 2|2 and resistance 2|8 to battery 2|6. This operates the armature of relay 2|2 so that its armature engages its right-hand which is received by sounder a breaking signal.

VAs a general proposition, it may be stated that, when inverse neutral repeaters are interconnected, a spacing signal transmitted toward the hub,

by any repeater connected to the hub, will result in the connection of ground to the hub and a spacing signal will be transmitted simultaneously from the hub through all of the other repeaters connected into the hub, and further, a permanent spacing' signal transmitted from any repeater While another repeater in the concentration group is transmitting toward the hub, will result in the loss of control, by the station which is transmitting, of the relay in the repeater which transmits toward the hub, when the station which is transmitting next sends a. marking signal toward the hub` The relay which transmits toward the hub will then be held to `marking and simultaneously the permanent spacing breaking signal will be transmitted to the station which was transmitting.

13 Circuit for permitting station connected into a half duplex concentration group to call switchboard The arrangement of Figs. 1, 2, 3 and 4 per Fig. A is equipped with a calling-in signal by means of which any loop station connected into the concentration group may signal the attendant who is administering the concentration group at the service board.

The three jacks .associated individually with each station loop and each telegraph line in any particular concentration group are all located in the same attendants positionl at the service board. The service board is a multiposition board. Various concentration groups are administered at various positions. The attendant in charge of a particular position controls a certain number of concentration groups such as the concentration group per Fig. A, comprising Figs. 1, 2, 3 and 4.

The manner in which an attendant at a station, such as station A, may summon an attendant at the position in the service board wherey tralize each other, so that the armature of re-V lay 206 remains in the condition shown. During the .transmission of a spacing or a break signal from station A, when the loop is opened, no current ows through either winding of relay 206. No current flows when a spacing signal is transmitted toward station A as both ends of the loop are connected to battery of the same polarity and magnitude for this condition. When the lower loop conductor is grounded and the upper loop conductor is opened, however, a circuit -may be traced from ground through sounder 209, make contact and armature of key 202, through the tip and break contact of jack 208, the break contact and ring of jack 201, the top winding of relay 206, the top winding oi relay 2|0, inductance coil 2| I, the armature-and left-hand contact of relay 212, resistance 2|3 and battery 2|4 to ground, operating relay 206. With relay 206 operated, a circuit may be traced from ground through the armature and front contact of relay 206, the .bottom armature and back contact of relay 220, conductor 222, which may be considered electrically as the hub of the calling-in circuit into Fig. 3, conductor 305, the back contact and armature of relay 306, through the winding of relay 301 in battery, operating relay 301 which locks from its bottom contacts under control of relay 306. The operation of relay 301 connects battery through .the top armature and front contact of relay 301 through the lament of lamps 308 and 309 in parallel to ground, lighting both of these lamps as a signal that some station associated in the concentration groups is calling in. One of vthese lamps, such as the primary appearance lamp 308, is located at the same position as the one in which the loop and line concentration jacks of the concentration group are located. The secondary appearance lamp 300 is located at an adjacent posivtion to provide the advantage of team work since with this arrangement any of four service board attendants may answer the ycall through the as.- sociated jacks.

Any other station, such as station B, connected Ithrough a station loop into the concentration group may light the same lamps 308 'and 309 by an operation similar to that described for station A, This should be apparent from reference to the station loop and loop repeater from station B. Ground from the armature of relay 206B is connected through the bottom armature and back contact of relay 220B .to conductor 222 in parallel with the ground from relay 206.

In response to the lighting of the lamps 308 or 300, the service board attendant administering the concentration group may connect an attendants telegraph transmitting and receiving set circuit operating on the inverse neutral principle to jack 3|0 or jack 3| This connecting circuit will not be described in detail hereunder as it does :not form part of the present invention. At this point attention is called to the fact that battery connected to the sleeve of the attendants circuit operates relay 306 over an obvious path. The operation of relay 306 breaks the operating path heretofore traced for the operation of relay 301 and relay 301 releases, extinguishing the lamps. The hub of the concentration gro-up, conductor 22|, is connected in multiple .to the tip of jacks 3| 0 and 3|| to provide a connection for the transmitting lead in the attendants circuit. By means of an inverse neutral repeater connected to the tip of jacks 3| it is possible for the attendant to transmit and receive signals to and from the various stations and lines comprising the concentration group or to monitor on all signals transmitted through hub 22 I.

The rings ci jacks 3|0 and 3|| are connected in multiple to the common calling-in or signal hub conductor 222. This is to provide a recall feature in the attendants connecting cord, A ,l

recalling operation is performed at a station in the same manner as a calling-in operation, If an `attendants cord circuit is already connected to either jack 3|0 or 3|| and any one of the Y stations connected into the concentration group through a station loop repeater wishes to again summon the attendants attention, the lower station loop conductor is grounded. This connects ground, in the manner already described, to Conductor 222 and to the ring of both jacks 3|0 and 3| This ground operates a relay in the attendants cord circuit connected to either jack to light a supervisory lamp as an indication that a station is recalling.

Connecting supervisor circuit and other circuits to concentration group Jacks 3|0 and 3H also provide means for establishing a connection to a supervisor. By means of a patching cord circuit it is possible to connect a test signal supply circuit to the concentration group through jacks 310 and 3| Also, jacks 3|0 and 3| may be used with suitable connecting circuits for the measurement of bias or distortion.

Releasing a Zine from a hal) duplex concentration group Because each telegraph line to a distant city and each telegraph loop to a local station appearing in the telegraph service board is terminated in its own individual inverse neutral repeater, it is possible in the system disclosed herein to make changes in a concentration group such as removing lines or loops, adding lines or loops or .remove a line or loop at the termination of its daily service period. The manner in which a telegraph line is disconnected from a concentration lgroup will now be explained. The east line will be used for` the purpose.

To perform this operation a control plug, such as plug 3|2, having its ring and sleeve conductors interconnected, is inserted into a cooperating jack, such as release control jack 3|3. This connects the ring and sleeve of jack 3I3.v A circuit may then be traced from ground, through the middle winding of relay 3| 5, to the sleeve of jack 3|3, through the sleeve of plug 3I2 to the ring of plug 3|2, through the ring of jack 3I3 and the top winding of relay 3|5, through battery 3I4 back to ground, operating relay SI5. The operation of relay SI5 connects ground through its upper armature and front contact and the wind- -ing of relay 30| to battery, operating relay 30|.

The operation of relay 30| breaks the connection -between the leg conductor and the hub 22| as previously traced, thus disconnecting the east line from the concentration group. The operation of relay also breaks the connection which extends from battery through the winding of relay I I3 in Fig. l, and conductor I I4, into Fig. 3,

. through the bottom middle armature and back lcontact of relay 30| and the top back contact and armature of relay 302 to ground, thus disconnecting ground formerly furnished through the top armature and back contact of relay 302. Relay I3 releases. This places the inverse neutral repeater in the east line in its normal condition which is the full duplex condition.

It has been explained that the circuit per Fig. 1 may function either full duplex or half duplex dependent upon whether it is connected into a full duplex or half duplex concentration group. When it was connected into the half duplex concentration group as explained above, it was conditioned to function half duplex through the operation of relay ||3. Now that it has been released, the repeater is restored to its normal full duplex condition. Even though it is no longer serving in the concentration group described above, it may be appropriated for use with another concentration group which may operate full duplex or half duplex. If the new concentration group is to operate full duplex, relay II3 will remain unoperated. If the new concentration group operates a half duplex, relay I I3 will be again operated.

To return to the operation of relay 30|, its operation sends a permanent spacing signal to the distant eastern terminal. This is performed as follows. A circuit may be traced from ground through the armature and back contact of relay 302, through the top inner frontcontact and armature of relay 30|, through conductor |32, through the left-hand back contact and armature of relay I I3, which is now released, through the bottom windings of relays IIS and H8,

through' resistances I|1 and ||6 and negative battery l5 back to ground. This operates relays H9 and II8, reversing the polarity of battery I2I as connected to the sending line and sending a permanent spacing signal to the distant eastern terminal.

The operation of rrelay 30|, also, by the transfer of its bottom innermost armature from its back to its front contact, disconnects ground from the sleeves of the multiple jacks 316, 3|'I and 3| 8 and connects the sleeves of these jacks to battery through the windings of relays 302 and 3I9. The object of the connection of ground to the sleeve While the line is connected into a concentration group was to permit monitoring on the circuit through a multiple jack. The plug of a monitoring circuit may be inserted into a multiple jack at any position in the board and ground on the sleeve of the multiple jack operates a relay in the monitoring circuit which conditions the monitoring circuit for monitoring. The purpose of the change from ground on the sleeve to battery through the relays will be understood from the description below.

The operation of relay 30| performs one other switching operation. It extends a circuit, which may be traced from ground, through the filament of lamps 32|, 322 and 323 in parallel, through the bottom outermost front contact and armature of relay 30|, through the bottom back contact and armature of relay 302 and through conductor 320 to a front contact of relay 40| in Fig. 4 which forms part of the idle indicator control circuit which will now be explained.

Idle indicator control circuit for indicating line avaiatlc for connection to concentration group It has been explained that each telegraph line connecting the service board to a distant city, whether connected into concentration jacks at a particular attendants position or not, is extended through a group of multiple jacks throughout the switchboard line-up. Some means must be provided for distinguishing between the lines which are serving as part of an operating concentration group and those which are available to be connected into a concentration group on a temporary basis by means of a patching operation. A line may be connected into a concentration group or it may be released from, or not connected to, a concentration group for relatively long intervals. If a lamp were lighted throughout either interval as anfindication of the condition, it would mean that many lamps would be burning in the switchboard at all times. This has a number of disadvantages including -battery drain, reduced life of lamps and reduced contrast between lighted and unlighted lamps, such as station calling-in signal lamps 308 and 309'described above.

In order to provide the advantages of a normally unlighted switchboard, and the other advantages enumerated above, the idle indicator control circuit is furnished. Its function is to light the lamps associated with all idle telegraph lines to distant cities momentarily, in response to the actuation of a key by an attendant who requires such a line, so that a selection of a line to a particular city may be made if such a line is available.

If an attendant at a particular position in the telegraph service board line-up requires a telegraph line to a distant city and Wishes to know which lines are availablev so that he may make a selection, the'attendant operates a key such as 402; Fig.v 4, at'the'particular attendants position. .Iherev is one such key at each position in the line-mp. Keys at other positions are indicated by keys. 403 and 404. VWhen key 402 is operated, relay 405 is operated over an obvious circuit. The operation of relay 405 closes a circuit from ground through the bottom front contact and armature of relay 405, through the winding of relay 406 and resistance 401 through battery to ground. Relay 406 will operate and lock up through its top middle front contact and armature to ground. The operation of relay 406 Will connect ground through its bottom inner front contact and armature and the winding of relay 40| to battery, operating relay 40|. The operation of relay 40| Will connect battery through its various contacts in parallel to a number of conductors extending to various leg multiple circuits.A Each of said conductors is arranged so that it may be multipled to a number of leg multiple circuits.` A circuit may be traced from battery through the top armature and front contact of relay 40|, through conductor 320, through the bottom armature and back contact of relay 302, through the bottom outermost armature and front contact of relay 30| and through the filaments of lamps 32|, 322 and 323 in parallel to ground, lighting each of the lamps, as an indication that the telegraph line circuit to a distant city associated with these lamps is available for use. Only such circuits as are available for use will have their associated idle indicating lamps lighted as the path to the lamps in the case of circuits which are not idle Will not be closed.

The lamps indicating that a circuit is available for use remain lighted for a` short interval only, While a selection of one of them is being made and then the lamps are extinguished through the operation of the idle indicator control circuit. The manner in'which this is performed will now be explained.

When relay 406 is operated a circuit may be traced from plate battery 408 through resistance 409 and conductor 4|0, through resistances 4|| and 4 I2 in parallel, through the bottom armature and front contact of relay 406, through the lament of lvacuum tube 4|3 and resistance 4|4 to ground, lighting the filament. After a momentary interval key 402 is released, in turn releasing relay 405. This removes ground which has been connected through the front contact and top armature of relay 405 to the upper terminal of condenser 4|5 and condenser 4|5 is charged over a path from battery 408 through resistance 409, through resistance 4|6 and the top innermost armature and front contact of relay 406 to the upper terminal of condenser 4|5, the bottom terminal of which is grounded. When the top plate of condenser 4|5 and the grid of tube 4|3, connected in parallel with the top plate of the condenser, have assumed a proper positive potential with respect to the cathode of tube 4|3, current will iloW through the plate circuit of the tube from positive battery 408, through resistance 409, through the winding of relay 4|1 to the plate of tube 4|3, from the plate to the filament of tube 4| 3 and through resistance 4|4 to ground, operating relay 4 l. The magnitude of resistance 4 6 and the capacity of condenser 4|5 establish the interval necessary to charge condenser 4|5 to the proper positive potential and the interval has been established for use with the idle indicating lamps of the inverse neutral circuits at appronmately six seconds.

When "relay 4|1 is operated, ground is con# nected to the left-hand terminal of resistance 401. This short-circuits the path through the Winding of relay 406 to ground, releasing relay 406. The release of relay 406 breaks the path heretofore traced through the lament of tube 4|3. The release of relay 406 also disconnects battery 40S from the top terminal of condenser 4|5. The battery connection of the condenser will be replaced by direct ground through the top outermost armature and back contact of relay 406 which will discharge condenser 4|5. When the lilament of tube 4|3 is extinguished current will no longer flow through the tube and relay 4|1 will be released. The` idle indicator control circuit is thus returned to normal.

If at any time a key such as 403 is operated momentarily, in turn operating relay 405 before the timing circuit has been permitted to complete its cycle, condenser 4|5 will be discharged from ground connected to the top front contact and armature of relay 405 and the entire timing cycle will be repeated.

Replacing a line forming part of a half duplex concentration group with aline which has been released from a, dierent concentration group The concentration group is arranged so that a line formingpart of a concentration group may be replaced by a second line. This second line may be a line which has been released from another concentration group or it may be a spare line. A spare line is one which is not normally connected into a concentration group, a spare line terminates in multiple jacks and a leg multiple. circuit, but it is not provided with a group of three concentration jacks and connected into a hub as is a line which is arranged to normally form part of a concentration group.

In this section the operation of replacing a line in a concentration group by a line which has been released from another concentration group will be described.

In order to replace a line forming part of a concentration group with a new line which has been released from a concentration group and is temporarily idle, first the idle indicating circuit described in the foregoing is operated, so that an idle line to the proper distant city may be indicated, if one is available, in order that the idle line may beselected for use. If such a line is available, the attendant, by means of a patching operation, through the leg patching cord circuit, shown at the right of Fig. 3, will connect the new line to the concentration group and, as a result of the patching operation, the old line will be automatically released from the concentration group and the new line will function in its'stead.

For the purposes of this explanation, it will be assumed that the line west has been previously released from another concentration group in another position of the board and it will be assumed that it connects at the distant end to the desired distant termination. The line west will be used to replace the line east.

Plug 324 will therefore be inserted into jack 3|6Wwhenlamp 32|W lights, indicating that the line is idle. Plug 325 will be inserted into jack 3|3. A` circuit may then be traced from battery through the windings of relays 3|9W and 302W in series, through the bottom innermost front contact and armature of relay 30|W, relay 30|W being operated While a line is released, through the sleeve of jack 3|6W, through the sleeve of 2,4113, cse

plug 324, sleeve of plug 325, sleeve of jack'3I3 and the low resistance middle Winding of relay SI to ground. Relays 3I9W and 302W operate in series with the low resistance middle Winding of relay SI5. Relay SI5 operates. The operation of relay 3 I 5 in turn operates relay 39 I. The operation of relay 39| breaks'the leg path from the east. line repeater into the hub 22| of the concentration group, disconnecting the east line from the concentration group and performs all of the other operations heretofore described attending the operation of this relay.

The leg of the new line repeater is connected through the tip of jack SIBW, tip of plug 324, tip and break contact of jack 32e, tip of plug 325, tip of jack 3I3, test resistance 303, break contact and armature of relay 304 into hub 22| to incorporate the line West into the concentration group.

It was pointed out that relays 3I'9W and 302W operated in-the West line which has replaced the east line in the concentration group. The operation of relay 3 I 9W connects ground to conductor IIfiW which extends into the Winding of a relay in the West inverse neutral repeater corresponding to relay I I3, which conditions the West repeater to function half duplex in the same manner as described for the east repeater. Relay 332W in operating in the new leg multiple circuit for the new line opens the idle indicating circuit for the West line as the West line has now been appropriated and disconnects ground from the leg of the repeater removing the permanent spacing signal which was transmitted to the distant Western terminal While the line Was idle. The operation of relay 302W also locks relay 3 I 5W from ground through its top armature and front contact to hold relay 3I5W operated, The reason for this is that the West line was made available for use by a releasing operation, such as just described above, or by means of inserting a control plug into a control jack, as previously described. This operation is performed at another position in a jack corresponding to jack 3I3W, namely at the particular position Where the concentration group With which the west line is assumed to be normally associated is administered. The removal of the releasing plug would release relay SI5-W and reconnect the West line into the concentration group With which it is normally associated. This is prevented by the locking of relay 3I5W when relay 302W operates.

The foregoing explains how a line released from the concentration group with which it is normally associated may be appropriated by an attendant to replace a line normally forming part of another concentration group.

The manner in which a lline which is normally spare, as distinguished from a line which is released from a concentration group with which it is normally associated, is connected into a half duplex concentration group as a substitute for a line forming part of a half duplex concentration group will now be explained.

Replacing a Zine fort-ning part of a, half duplex concentration group with a spare Zine As stated above, spare lines are distinguished from lines ordinarily forming parts of concentration groups, in that spare lines appear only in multiple jacks at each attendants position and are not extended through their leg multiple circuits into three individual concentration jacks at a particular position, through which they are extendedto a hub so that they normally form part. of a 'particular'y concentration group'.` A spare line; may be. appropriated, by means of a patching operation from one of its multiple jacks. at any position, toa particular jack in a line normally forming part of a` concentration group, to

- replace a line normally forming part of a concentration group.

In order to replace aline normally forming part of a concentration group with a spare line, a. patch is made from a multiple jack of the spare line to the control jack of the line which is to be replaced.

For purposes of this vexplanation it will be as.- sumed that the West line is now a spare line. In order that the West line may simulate a spare line, it will be assumed that its relay 3U IW is permanently operated. Each spare line throughout the board isV arranged so that electrically it is the equivalent' of a line which normally forms part of a concentration group, except that each of the circuits extending through the4 various armatures of its relay corresponding to relay 33IW is closed through its respective front contact instead of through its back contact as shown for the normal unoperated condition of relay 3Q IW in Fig'. 3. Further, a. 4spare line is not provided With a concentration jack circuit.

It will be assumed that the spare West line is to be used to replace the east line which normally forms part of a half duplex concentration group. First the idle indicator circuit is operated and a lampv such as 32fI'W is lighted indicating that the line is available. The plug 324 is inserted into jack 3I3W and plug4 325 isv inserted into jack 3I3.

As a result of this operation the tip of the spare line is extended into the hub of the concentration group in the same manner as described above. The sleeve of the spare line is extended over a circuit, exactly the same as described before, for a released line, starting from battery connected to. relay 3I9W in the spare line and ending in ground connected to relay 3I5 in the replaced east line. Relays 3I9W, 302W and 3I5 are operated in series. Relay 3I9W in operating conditions the repeater in the west line to function half duplex as described heretofore. Relay 352W in operating. disconnects the idle indicating circuit at its bottom armature and front contact. The operation of relay 302W also operates relay 3I3W as described above, but this performs no useful function in the case of a spare circuit, as'it did in the case of a released circuit described above. The operation of relay 3I5 releases the replaced line from the concentration group.

Adding a released. Zine to a half duplex concentration group tration group. This operates relay 3| 5W in turn operating relay SEIIW in the manner heretofore described.

The attendant who desires to add a line operates the idle indicating key at the position where the concentration group to which the line is to be added is administered. Once again the idle indicating lamps of all available lines are lighted.

In order to add the west linev to theconcentration of which the east line forms a part, the attendant'inserts plug 32d into line multiple jack 3|6W when lamp 32|W lights. Plug 325 is inserted into jack 321. 1

As a result of this operation the tip of 'the West line is connected through the tip of jack 3|6W, tip of plug 324, tip and break contact or jack 325, tip of plug 325 and tip of jack. 321 to hub 22|. This connects the transmission conductor of the West line into the concentration group of which the east line forms a part.

yA circuit may also be traced from battery through the winding of relay 3i9W, Winding of relay 302W, bottom innermost front contact and armature of relay SWW, relay `"WIW being operated when the West line is released in a manner heretofore described, through the sleeve of jack 3|6W, sleeve of plugs 324 and 325 and sleeveof jack 32'! to direct ground. This operates relays 3|9W and 3ii2Wwhich conditions the west line for half duplex operation, disconnects the idle indicator lamp circuit and provides ground to hold relay 3|5W operated in the samemanner as heretofore described. p

-It should be observed that in the operation oi addinga line, adiirerent jack in the line concentration jack circuit normally forming part of a concentration group is used than the jack which is used for releasing a line or for replacing a line forming part of aconcentration group with a released line or a spare line. All of these latteroperations involve a releasing operation, which' must be performed by connection to a jack such as 3|3 which controls the operation of the releasing relay such as 3|5. When a line is to be simply added to a concentration group, connection is made to jack such as 32'! and the releasing relay remains unaffected.

Adding a spare Zine to a half duplex concentration group A spare line may be added to a concentration group. It will be again assumed that the West line is a spare line. That is, it is not provided with a group of individual concentration jacks and its relay 3B |W is blocked operated.

The attendant, at the position Where the conc entration group to which the spare line is to be added is administered, operates the idle indicator control circuit and, when all of the lamps associated with idle lines light, selects the spare west line for addition to the particular concentration group of which the east line forms a part.

Plug 324 is inserted into jack 3|6W and plug l 325 is inserted into jack 32'! of the east line. The

tip of the West line is connected into the hub over a vcircuit heretofore traced. Y Relays 3|9W and 3l2 W operate in the samemanner and perform the same functions as describedabove. The west line thus becomes a part of the concentration group with which the east line is normally asso'- ciated.

lSupervision in half duplex lpatching operations lights in response to the operation of a key such;

plug 325 into a multiple jack, such as Slt and,

plug 325 into jack 553 of Fig. 5. With these circuits interconnected in this manner, the conductor over which communication signals are received over the line circuit incoming from the distant ofiice is extended through the tip of multiple jack 3|3, tip of plug 324, tip and break contacts of jack 326, tip of plug 325, tip of jack 563, tip of jack 502', tip of plug 53| and into the telegraph cord circuit, Where it passes ultimately through the Winding of a telegraph receiving relay such as 507, to negative battery. At the same time ground is connected through the sleeve of jack M33, sleeve ofy plug 325, .sleeve of plug 324, sleeve of jack 3M, through the bottom innermost contact of relay 33| which is operated, and the windings of relays 302 and 3|?) to battery. Relays 3H) and 3BE operate from the direct ground on the sleeve of jack 5fl3. This operation of relay 3M removes ground from the path heretofore traced through the windings'of relays |-9 and H8 to negative battery H5. This results in the removal 'of the permanent spacing signal which Was being transmitted to the distant terminal over the east line and a change of relays |9 and |i8 to marking. The operation of relayk 3|3 operates relay i l-li which changes the line repeater from the full duplex to the rhalf duplex condition.

When the marking signal is received at the distant terminal, the attendant thereat may respond in such manner that the permanent spacingcondition imposed at the distant office on relays lill and |2 is removed and changed to marking. As a result of this, relays |06 and ||2 are in turn changed to the marking condition. When ground is removed from the armature of relayv H2, the permanent spacing signal is removed from conductor |25) and the tip circuit' plug 325 from jack, 503 and connects it instead into a jack in a line circuit of the concentration group such as jack 3|3W or 321W vdepending upon Whether the line is to replace an existing line in a concentration group or be added to a concentration group.l

Releasing a. station circuit from c half duplex f concentration group Station loops normally connected to a concentration group may be released from the concentration group forl test purposes, or for transfer to other concentration groups or because their daily Working period is ended. To perform this operation, a plug such'as 3|2 having its ring and sleeve conductors interconnected is inserted in ajack such as 224.

A circuit path is established as a result of the caracas-f above operation extending from ground,l through the sleeve of jack 224, sleeve of plug 3I2, ring of plug 3|2, ring of jack 224 and bottom Winding of relay 220 to battery, operating relay 223. The operation of relay 223 disconnects the station from the concentration group, by disconnecting the loop repeater transmission lead from the hub 22| at the top armature and back contact. of relay 220 and disconnecting the loop calling-in lead at the bottom armature and back contact of relay 22B.

Adding a station circuit to a half duplex concentration After a loop has been disconnected from a concentration group it may be added to a different concentration group by inserting the plug 324 into a jack such as 225 and the plug 325 into a line jack such as 321. This extends the tip or transmission conductor of the loop repeater through the tip of jack 225, tip of plug 324, tip and `break contact of jack 323, tip of plug 325, tip of jack 321, into the hub 22| of the concentration group. It also extends the loop repeater calling-in conductor through the ring of jack 225, ring of plug 324, make contact of key 333, which is operated for this purpose, ring of plug 325, ring of jack 321 into the common calling-in conductor or signal hub 222.

While a station loop repeater is released, con nection may be made to jacks such as 225 for testing purposes. This provides access to both the transmission conductor and the calling-in conductor of the loop repeater. Ground on the sleeve of the jack 225 is provided for controlling relays in the sleeves of coopera-ting testing cord or jack circuits.

Transmitting good night or permanent spacing signal When a station loop repeater isV released, it.

may be arranged to transmit a permanent spacing or good night signal toward the station by inserting a control plug such as 328 into a jack such as 225. This connects ground from the sleeve of jack 225, sleeve of plug 328, tip of plug 328, tip of jack 225 to the transmission conductor of the loop repeater which transmits a permanent spacing signal to the station.

If it is desired to transmit a good night or permanent spacing signal over all of the circuits formed into a concentration group', a plug having its tip and sleeve conductors interconnected, such as 328, may be inserted into jack 321.

A circuit is established under the above condition which may be traced from ground through the sleeve of jack 321, sleeve of plug 328, tip of plug 328, tip of jack 321, into the hub conductor 22 I. As has been shown, a ground connected to the hub of the concentration group transmits a spacing signal over each line and loop leg formed into the concentration group.

Further, since the tip of jackv 321V is' common to the hub, a monitoring circuit, not shown, may be connected to jack 321 and signals may be. received in the monitoring circuit from the hub over the tip of jack 321 and through the tip of the plug of the monitoring circuit.

Provision for testing andV observing hits on a Zeg in a, half duplex concentration group Jacks 223, 223B, 329, 329W and 323 provide means .for connecting a testing circuit to a line or loop legand testingl it separately'from the con-v centration group and for observing for hits byl means. of." a troublel indicator cord circuit, not

shown. Whether a line or a loop leg is normally' associated With a concentration group, or, inthe case of a line, is serving as a substitute in a concentration group, connection of a trouble indicator cord circuit to jacks such as 329, 223 or 326 will permit observation for hits occuring on the associated leg. When a line or loop leg is added to a concentration group through the medium of the patching cord terminating in plugs 324 andy 3.25, such observations will be obtained through jack 326.

Attention is particularly called to the resistances 2H) and 2|9B in Fig. 2 and 303, 303W and 333 in Fig. 3. One end of each of these resistances is connected to a tip conductor of one of each of the above jacks. The opposite end of each of these resistances connects through the contacts or the test relay to a ring conductor of the corresponding jack. These resistances are connected in series in the leg lead in each instance. When signals are being received from a leg, a potential drop in a particular direction occurs in its associated resistance. When signals are being sent tothe leg through the resistance, the drop is in the reverse direction. Further, when signals received from one leg are sent to a group of legs associated together in a concentration group, a greater current ows in this leg than when it is sending to a line or loop. The drop for'the rst of these conditions is therefore greater. This assumes that at least three repeater legs are joined in a concentration group. If a linear loop is in trouble, so that it is causing random false spacing signals to be transmitted toward the hub, this condition may be detected by connecting to jacks, such as 223, 223B, 323 and 329W, a device which is responsive to changes of potential across two points and which discriminates between such changes in reverse direction.

Relays 220, 223B,v 334, 304W, and 334 each have a winding connected between ground and the sleeve of an associated jack. These relays are arranged so that they may be operated or remain released, depending upon the resistance f inserted in the connection to battery in the sleeve circuit of the cooperating cord circuit. When a trouble indicator cord circuit is connected to any one of the jacks for the purpose of observing hits on. the associated leg, since the trouble indicator cordV is arranged to respond' to a drop across the test resistance in a particular direction, the resistance must remain in circuit and the test relay remains unoperated.

Jacks 2723, 223B, 329, 329W and 326 also plO- bined for communication, may be connected bymeans of aV plug to the ring conductor of each of these jacks.r Under these circumstances, if it is desired to monitor on the whole concentration` group or` communicate over the whole concentration group', the resistance or the connected sleeve. circuit Will be high to prevent the operation of the relays, such as 220, 394 and 334.

If it is desired to split the leg of a loop or aline oil" from a concentration for testing it separately, connection is made to jacks such as 223i, 329 and 325 and the sleeve of the connecting. circuitis. arranged so that it connects to battery" through. a. low resistance. to permit testreu lays? such as` 228, 334 and 334 to operate. vThis disconnects the associated leg from the concentration group. The leg is extended through the associated tip conductor and the hub 22| through the associated ring conductor of the cooperating jack into the connected circuit for testing. By connecting the inverse neutral repeater in the cooperating connected circuit through a splitting key, it is possible to communicate with the leg which has been out offrom the hub over the tip or with the circuits which remain associated in the concentration group over the ring'of jacks such as 223, 329 and 326.

FULI. DUPLEX CONCENTRATION GROUP A full' duplex concentrationgroup will now be described. v

In a. full duplex concentration group, separate independent hubs are required for transmission in opposite directions. The sending loops, receiving loops and lines may be connected together in various ways, depending upon the trafllc requirements. The arrangement to be described will therefore be a typical arrangement. In this typical arrangement, a telegraph service board will be used to interconnect an east line, a westline and a local patrons station. Full duplex service is provided between the east terminal and the west terminal over` the east and west lines in tandem. The patrons station is equipped with two loops for full duplex operation.

For full duplex operation, Figs. 1, 6, '1 and 4 are arranged as indicated in the rectangular box Fig. B, .bearing the legend Full duplex concentration group. This exemplifies a typical arrangement including two lines and a local station comprising two loops. The two lines may be assumed to be an east line, which extends to a distant eastern terminal, and a west line which extends to a distant western terminal.

Although the detailed description will again assume the use-of four-wire metallic line circuits, it should be understood that carrier line circuits, two path polar circuits or differential duplex line circuits may be used when terminated in the proper inverse neutral type of repeater which provides separate send and receive legs on the dropsida The legs appear inleg multiple circuits as previously described and each legis extended from the leg multiple circuit through a line concentration jack circuit to a hub. -The sending leg of one line is connected through the hub to the receiving leg of the other line in each instance.

Since two hubs are required in full duplex operation, one for east-to-west transmission and one for west-to-east transmission, in order to provide a subscribers local station with full duplex scribers premises with an individual inverse neutral loop repeater at the service board terminal. tis extended via the leg of the loop repeater into -an individual concentration vjack circuit. lFrom this loop concentration jack circuit it is connected into one of the two hubs. l

In asimilar manner a second sending andreceiving instrument on the subscribers premises is connected rthrough afloopcircuit to anindl vidual inverse neutral loop repeater.l It is extended via the leg of thelooprepeater intoanv `may transmit to the west terminal.

vsuch as i I5..

hub'1ll4 to a receiving west terminal;

Thus', there is an individual hub and conceny tration group for transmitting in each direction. Both are independent.

In the case of full duplex operation, the concentration group for the east-to-west hub and the concentration group for the west-to-east hub are located at the same attendants position at the telegraph service board. If it is desired, a multiple appearance of the concentration jacks may be provided at a second attendants position. The leg' multiple jacks of the line circuits and the idle indicator lamps and control circuit are arranged in the same manner as described above for a half duplex concentration group.

Refer now to Figs. 1, 6, 7 and 4 arranged for full duplex operation. In the numbering of the apparatus for a full duplex concentration group,

numbers only, without any letter suflixes, will be used as both station loops extend to the station of but one patron and the sending leg oi one line repeater is connected to thelreceiving leg of its cooperating line repeater.

It was shown in the description above that the east line'in Fig. 1 was convertible from a full duplex to a half duplex and Vice versa. Itwas shown that when a linewas released from a concentration group or serving as a spare line, the relay such as l I3 in the line repeater was released and the line repeater was conditioned to function as a full duplex repeater. In such case two separate legs extended fromthe repeater through the leg multiple circuit. Onthe other hand, when a line was normally connected toa half duplex -concentration group, relay H3 was operated and only one Vleg from the line repeater was used, in

Ywhich vrease sending and receiving was performed over the single leg.v In the arrangement nowto be described, the line is normally connected into a full duplex concentration group Under such a condition relay H3 remains released and two legs extend from the line repeater through the leg multiple circuit and into separate line concentration jacks for eachleg. To provide for the four line legsfrom the two lines, four-sets of line concentration jacks are required. When signals -a're transmitted' from the distant terminal to the 104 which is the east-to-west hub.

The send leg, by means of which signals are transmitted to the distant west terminal, is connected to the same hub, so that .the east terminal The circuit' may be traced from hub 104, through the armature and back contact of relay 133, resistance 186, :through the top inner back contact and armatureof relay 101, through conductors 136, E36 and 136 into the rectangle exemplifyi'ng the west repeater and line. There the path will be continuedv through the left-hand break contact and armature of a relay such as H3 (which remains released) ,through Athe bottom windings of relays such as H3 and l I8 in series, through resistances such'as YI l1 and .I i5 in series to negative. battery rE'hus signals impressed on relays IEM Yand [B12 at .the east terminal pass through relay such as i 21 at the In a similar manner, signals impressed onre lays such as and |02 at the west terminal connect negative battery and ground for marking and spacing through the contacts of a relay such as ||2 in the west repeater. These signals are impressed. through conductors |3|, 63| and 13|, through the top outer armature and back contact of relay 101, through resistance 108`to -l'lulb m5, which is the west-to-east hub. From hub 105 a path may be traced through the armature and back Contact of relay 109, resistance 1|0, too inner back contact and armature of relayy i, conductors 132, E32 and |32, left-hand back contact and armature of relay ||3, bottom windings of relays H9 and H8, resistances |l1and H8 to negative battery I i5. This results, as haslbeen previously shown, in the reception of signals by receiving relay |21 at the east terminal.

One loop from the local station is connected through an individual loop repeater and an individual group of concentration jacks to hulb 104,

and the other through corresponding facilities to hub 105.

In' the station circuit shown in Fig. 6 there is a telegraph key and a sounder in each loop. vThe equipment in the station loops may be'. varied to suit conditions. For example, where a station circuit is to be restricted to receiving only, the equipment on the loop would comprise only a sounder. The polar relay, by means of which the inverse neutral repeaterv receives signals transmitted from the local station and transmits them toward the hub, would be blocked in the mark position or would be removed from itsjack mounting and replaced with a dummy relay basestrapped to obtain the same effect. Such loops would not be equipped for calling in the service board attendant', hence the callsignal key, at the station, corresponding to key 221 in Fig. 2 and the diierentially connected relay, such as 206 in Fig. 2, would be omitted. v

.With the concentration group described, the east and west line may communicate on a full duplex basis. Signals transmitted from the east to the West terminal will be recorded by thesounder in one loop at the local station. Signals transmitted from the west to the east terminal will be recorded by thereceiving instrument in the other loop at the local station. The telegraph key in one loop at the local station may be used to com municate with the east terminal. The transmitter in the other loop at the local station may be used to communicate with the west terminal.

Attention was called above to the fact that the connections for full duplex service .are widely variable dependent on the trai'lic desired. As an il'- lustration, it is possible to connect a group of lines such as described herein,v so that they radiate from a service board in many directions and to interconnect vall of their sending legs into a common hub. A loop from a local station havingfa transmitting instrument could be connected to the common hub to establish a broadcast arrangement. All of the receiving legs of line repeaters from the various distant terminals could be connected into a common hub and extended through a separate loop tothe receiving instrument at the local station. Transmission from the various distant stations to the local station could be `scheduled on a time basis to prevent interference or, if one distant terminal Were transmitting to the local static-n and a second distant terminal started to transmit simultaneously, the local station could signal over itsbroadcast transmitter that the station receiver was busy.

".eleasimirl a Zine from a full duplex concentration Y group erating relay 1|2. The operation'of relay 1|2 in turn operates relay 10| over an obvious circuit, to break the connections of they send and receive legs of the east line from hubs '05 and 104 at the top inner armature and back contact and top outer armature and back contact, respectively, of relay 10|.

The West line may be released by a similar operation performed in a corresponding jack in the west line.

Replacing a Zine forming part of a full duplex concentration group vwith a Zine which has been released from a dz'erent concentration group In order to substitute a released line for a line normally vforming part of a full duplex concentration group, it is irst necessary to find a released idle line to the desired distant terminal which is available to serve as a substitute. In the case of all idle lines, both released and spare, a path is closed -from ground connected to the lilaments of the idle indicating lamps of each circuit in multiple, through its associated leg multiple circuit, to battery in the idle indicator control circuit. The attendant operates the idle indicator control key at the position where the concentration group is being administered. This lights the multiple lamps of every telegraph line in the service board which is not at the moment serving in a concentration group. The attendant selects one connected to the desired distant terminal from reference to a designation strip associated with the lighted lamps. A patch is made from the multiple jack associated with the available line, at the attendants position Where the concentration group is administered to the control jack of the line in the full duplex concentration group vvhich is to be released and replaced by the new line. This automatically releases the old line and connects the two legs of the new line intol the two hubs.

It will be assumed, in order to demonstrate this operation, that the concentration group consists of the west line and the local station loops. It will be assumed also that the east line is idle. The east line, it will be assumed, normally forms part of another concentration group instead of the concentration group described above, from which other concentration group it has been released by an operation such as described in the preceding section herein.

tered. A ring sleeve short circuitingplug would have been inserted in jack 1|| at that position.

'Relays 1 2 and 10| would be operated.

The attendant at the position where the con- 

